The inventory interface is BookInventory. Package declaration, imports, and Javadocs have been removed for clarity:

public interface BookInventory
{
enum SearchCriteria
{
ISBN_LIKE,
TITLE_LIKE,
AUTHOR_LIKE,
GROUP_LIKE,
GRADE_GT,
GRADE_LT
}
Set<String> getCategories();
MutableBook createBook(String isbn)
throws BookAlreadyExistsException;;
MutableBook loadBookForEdit(String isbn)
throws BookNotFoundException;
String storeBook(MutableBook book) throws InvalidBookException;
Book loadBook(String isbn) throws BookNotFoundException;
void removeBook(String isbn) throws BookNotFoundException;
Set<String> searchBooks(
Map<SearchCriteria, String> criteria);
}

The method getCategories gives back the list of book categories.

The method createBook is the factory method. It is used to create a new book for a given ISBN and throws a BookAlreadyExistsException if a book with that ISBN is already inventoried. The loadBookForEdit method will retrieve a book that's already created or throw a BookNotFoundException if the book is not in the inventory.

Both of these methods will return a MutableBook as the intention is to edit the book and then store it using the storeBook method.

The storeBook method saves changes made to a book. It will check that the book has all mandatory attributes set and throw an InvalidBookException if it's not the case. It returns the ISBN of the book that was stored.

The loadBook method loads an existing book, given its ISBN reference. It returns a read-only Book or throws a BookNotFoundException if no book was previously stored with this particular ISBN reference.

The removeBook method removes a book from the inventory, based on its ISBN reference, or throws a BookNotFoundException, if no book was previously stored with this ISBN reference.

The exceptions are straightforward and are not listed here.

The searchBooks method finds the books in the bookshelf that match a given set of criteria. It returns the set of ISBNs for the books that match the search criteria. They are as follows:

For example, if we want to search for all books from "John Doe", which we assigned a grade higher than 5, we would call:

Map<SearchCriteria, String> criteria =
new HashMap<SearchCriteria, String>();
crits.put(SearchCriteria.AUTHOR_LIKE, "John Doe");
crits.put(SearchCriteria.GRADE_GT, "5");
Set<String> results = impl.searchBooks(crits);

The Book Inventory API is now ready to be bundled.